Chilling-induced tomato flavor loss is associated with altered volatile synthesis and transient changes in DNA methylation
Saturday, 2016/11/05 | 06:05:42
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Bo Zhang, Denise M. Tieman, Chen Jiao, Yimin Xu, Kunsong Chen, Zhangjun Fe, James J. Giovannoni, and Harry J. Klee SignificanceCold storage is widely used to extend shelf-life of agriculture products. For tomato, this handling results in reduced flavor quality. Our work provides major insights into the effects of chilling on consumer liking, the flavor metabolome and transcriptome, as well as DNA methylation status. Transcripts for some key volatile synthesis enzymes and the most important ripening-associated transcription factors are greatly reduced in response to chilling. These reductions are accompanied by major changes in the methylation status of promoter regions. Transient increases in DNA methylation occur during chilling. Our analysis provides insight into the molecular mechanisms of tomato fruit flavor loss caused by chilling. AbstractCommercial tomatoes are widely perceived by consumers as lacking flavor. A major part of that problem is a postharvest handling system that chills fruit. Low-temperature storage is widely used to slow ripening and reduce decay. However, chilling results in loss of flavor. Flavor-associated volatiles are sensitive to temperatures below 12 °C, and their loss greatly reduces flavor quality. Here, we provide a comprehensive view of the effects of chilling on flavor and volatiles associated with consumer liking. Reduced levels of specific volatiles are associated with significant reductions in transcripts encoding key volatile synthesis enzymes. Although expression of some genes critical to volatile synthesis recovers after a return to 20 °C, some genes do not. RNAs encoding transcription factors essential for ripening, including RIPENING INHIBITOR (RIN), NONRIPENING, and COLORLESS NONRIPENING are reduced in response to chilling and may be responsible for reduced transcript levels in many downstream genes during chilling. Those reductions are accompanied by major changes in the methylation status of promoters, including RIN. Methylation changes are transient and may contribute to the fidelity of gene expression required to provide maximal beneficial environmental response with minimal tangential influence on broader fruit developmental biology.
See: http://www.pnas.org/content/113/44/12580.full PNAS November 8 2016; vol.113; no.44: 12580–12585
Fig. 1. Changes in Ailsa Craig sugars, organic acids (mg⋅g−1 FW) and volatiles (ng⋅g−1 FW h−1) in response to cold storage. (A) Effect of cold storage on sugar and organic acid content. (B) Changes in volatiles derived from various pathways. Day 0, red ripe tomato fruit at harvest; C8d, fruit following 8 d of cold storage; C7dS1, fruit stored in the cold for 7 d followed by a 1-d recovery at 20 °C. Significant differences (P < 0.05) are denoted by letters. Error bars indicate means ± SE; three biological replicates. |
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